A woman carries a child through a field near the collapsed Plaza Towers Elementary School in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile wide with winds up to 200 mph roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo Sue Ogrocki) less

A woman carries a child through a field near the collapsed Plaza Towers Elementary School in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile wide with winds up to 200 mph roared through the ... more

Photo: Sue Ogrocki, Associated Press

A woman carries a child through a field near the collapsed Plaza... Photo-4657202.62850 - San Antonio Express-News

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A tornado passes across south Oklahoma City, Monday, May 20, 2013. A monstrous tornado roared through the Oklahoma City suburbs, flattening entire neighborhoods with winds up to 200 mph, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/The Oklahoman, Paul Hellstern) less

A tornado passes across south Oklahoma City, Monday, May 20, 2013. A monstrous tornado roared through the Oklahoma City suburbs, flattening entire neighborhoods with winds up to 200 mph, setting buildings on ... more

Photo: Paul Hellstern, Associated Press

A tornado passes across south Oklahoma City, Monday, May 20, 2013.... Photo-4657404.62850 - San Antonio Express-News

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Tiffany Bauman comforts a dying dog injured by Monday's tornado in the neighborhood of Westmoor, near Moore, Okla., May 20, 2013. A huge tornado, perhaps a mile wide, tore through towns near Oklahoma City on Monday, killing at least 37 people and sending rescuers and residents dashing to dig out survivors buried in rubble. (Nick Oxford/The New York Times) less

Tiffany Bauman comforts a dying dog injured by Monday's tornado in the neighborhood of Westmoor, near Moore, Okla., May 20, 2013. A huge tornado, perhaps a mile wide, tore through towns near Oklahoma City on ... more

A child calls to his father after being pulled from the rubble of the Tower Plaza Elementary School following a tornado in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile (1.6 kilometers) wide with winds up to 200 mph (320 kph) roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on the elementary school. (AP Photo/Sue Ogrocki) less

A child calls to his father after being pulled from the rubble of the Tower Plaza Elementary School following a tornado in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile (1.6 kilometers) wide ... more

Photo: Sue Ogrocki, Associated Press

A child calls to his father after being pulled from the rubble of... Photo-4657207.62850 - San Antonio Express-News

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Taboola Gallery Frame Item-85307.62850 - San Antonio Express-News

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This aerial photo shows the remains of homes hit by a massive tornado in Moore, Okla., Monday May 20, 2013. A tornado roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/Steve Gooch) less

This aerial photo shows the remains of homes hit by a massive tornado in Moore, Okla., Monday May 20, 2013. A tornado roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting ... more

Photo: Steve Gooch, Associated Press

This aerial photo shows the remains of homes hit by a massive... Photo-4658651.62850 - San Antonio Express-News

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Teachers carry children away from Briarwood Elementary school after a tornado destroyed the school in south Oklahoma City, Monday, May 20, 2013. A monstrous tornado roared through the Oklahoma City suburbs, flattening entire neighborhoods with winds up to 200 mph, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/The Oklahoman, Paul Hellstern) less

Teachers carry children away from Briarwood Elementary school after a tornado destroyed the school in south Oklahoma City, Monday, May 20, 2013. A monstrous tornado roared through the Oklahoma City suburbs, ... more

A fire burns in the Tower Plaza Addition in Moore, Okla., following a tornado Monday, May 20, 2013. A tornado as much as a mile wide with winds up to 200 mph roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/Sue Ogrocki) less

A fire burns in the Tower Plaza Addition in Moore, Okla., following a tornado Monday, May 20, 2013. A tornado as much as a mile wide with winds up to 200 mph roared through the Oklahoma City suburbs Monday, ... more

Rescuers recover a horse from the remains of a day care center and destroyed barns, Monday, May 20, 2013 in Moore, Okla. A monstrous tornado roared through the Oklahoma City suburbs, flattening entire neighborhoods with winds up to 200 mph, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/The Oklahoman, Steve Sisney) less

Rescuers recover a horse from the remains of a day care center and destroyed barns, Monday, May 20, 2013 in Moore, Okla. A monstrous tornado roared through the Oklahoma City suburbs, flattening entire ... more

Photo: Steve Sisney, Associated Press

Rescuers recover a horse from the remains of a day care center and... Photo-4658773.62850 - San Antonio Express-News

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Taboola Gallery Frame Item-85307.62850 - San Antonio Express-News

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CORRECTS TORNADO MEASUREMENT TO NUMBER REPORTED BY THE NATIONAL WEATHER SERVICE - A woman is pulled out from under tornado debris at the Plaza Towers School in Moore, Okla., Monday, May 20, 2013. A tornado as much as half a mile (.8 kilometers) wide with winds up to 200 mph (320 kph) roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school.(AP Photo Sue Ogrocki) less

CORRECTS TORNADO MEASUREMENT TO NUMBER REPORTED BY THE NATIONAL WEATHER SERVICE - A woman is pulled out from under tornado debris at the Plaza Towers School in Moore, Okla., Monday, May 20, 2013. A tornado as ... more

Photo: Sue Ogrocki, Associated Press

CORRECTS TORNADO MEASUREMENT TO NUMBER REPORTED BY THE NATIONAL... Photo-4658772.62850 - San Antonio Express-News

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This aerial photo shows the remains of homes hit by a massive tornado in Moore, Okla., Monday May 20, 2013. A tornado roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/Steve Gooch) less

This aerial photo shows the remains of homes hit by a massive tornado in Moore, Okla., Monday May 20, 2013. A tornado roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting ... more

Photo: Steve Gooch, Associated Press

This aerial photo shows the remains of homes hit by a massive... Photo-4658771.62850 - San Antonio Express-News

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Rebekah Stuck hugs her son, Aiden Stuck, 7, after she found him in front of the destroyed Briarwood Elementary after a tornado struck south Oklahoma City and Moore, Okla., Monday, May 20, 2013. Aiden Stuck was inside the school when it was hit. (AP Photo/ The Oklahoman, Nate Billings) less

Rebekah Stuck hugs her son, Aiden Stuck, 7, after she found him in front of the destroyed Briarwood Elementary after a tornado struck south Oklahoma City and Moore, Okla., Monday, May 20, 2013. Aiden Stuck was ... more

Photo: Nate Billings, Associated Press

Rebekah Stuck hugs her son, Aiden Stuck, 7, after she found him in... Photo-4658751.62850 - San Antonio Express-News

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Antonio Flores of Moore, Okla. searches for his car after a tornado damaged the Moore Medical Center and the vehicles in the parking lot in Moore, Okla. on Monday, May 20, 2013. (AP Photo/Alonzo Adams)

Antonio Flores of Moore, Okla. searches for his car after a tornado damaged the Moore Medical Center and the vehicles in the parking lot in Moore, Okla. on Monday, May 20, 2013. (AP Photo/Alonzo Adams)

Photo: Alonzo Adams, Associated Press

Antonio Flores of Moore, Okla. searches for his car after a tornado... Photo-4658756.62850 - San Antonio Express-News

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Taboola Gallery Frame Item-85307.62850 - San Antonio Express-News

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Tiffany Bauman comforts a dying dog injured by Monday's tornado in the neighborhood of Westmoor, near Moore, Okla., May 20, 2013. A huge tornado, perhaps a mile wide, tore through towns near Oklahoma City on Monday, killing at least 37 people and sending rescuers and residents dashing to dig out survivors buried in rubble. (Nick Oxford/The New York Times) less

Tiffany Bauman comforts a dying dog injured by Monday's tornado in the neighborhood of Westmoor, near Moore, Okla., May 20, 2013. A huge tornado, perhaps a mile wide, tore through towns near Oklahoma City on ... more

Two men attempt to pry open a door on this car to check for victims in a business parking lot west of I-35 south of 4th Street in Moore, on Monday, May 20, 2013.A monstrous tornado roared through the Oklahoma City suburbs, flattening entire neighborhoods with winds up to 200 mph, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/The Oklahoman, Jim Beckel) less

Two men attempt to pry open a door on this car to check for victims in a business parking lot west of I-35 south of 4th Street in Moore, on Monday, May 20, 2013.A monstrous tornado roared through the Oklahoma ... more

Photo: Jim Beckel, Associated Press

Two men attempt to pry open a door on this car to check for... Photo-4658634.62850 - San Antonio Express-News

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This aerial photo shows the Moore Medical center in Moore, Okla., following a tornado Monday, May 20, 2013. A tornado roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/Steve Gooch) less

This aerial photo shows the Moore Medical center in Moore, Okla., following a tornado Monday, May 20, 2013. A tornado roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting ... more

This aerial photo shows the remains of homes hit by a massive tornado in Moore, Okla., Monday May 20, 2013. A tornado roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/Steve Gooch) less

This aerial photo shows the remains of homes hit by a massive tornado in Moore, Okla., Monday May 20, 2013. A tornado roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting ... more

Photo: Steve Gooch, Associated Press

This aerial photo shows the remains of homes hit by a massive... Photo-4658637.62850 - San Antonio Express-News

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Taboola Gallery Frame Item-85307.62850 - San Antonio Express-News

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Moore police dig through the rubble of the Plaza Towers Elementary School following a tornado in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile (1.6 kilometers) wide with winds up to 200 mph (320 kph) roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/Sue Ogrocki) less

Moore police dig through the rubble of the Plaza Towers Elementary School following a tornado in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile (1.6 kilometers) wide with winds up to 200 mph ... more

Photo: Sue Ogrocki, Associated Press

Moore police dig through the rubble of the Plaza Towers Elementary... Photo-4657206.62850 - San Antonio Express-News